NSD Achieves Energy Goals with FOG Collection

May  17, 2013

These days, it seems like just about everything that was once considered a waste product is fast becoming valuable. Even the fats, oils and grease (FOG) cleaned out of a restaurant’s grease trap has become a hot commodity.

The Napa Sanitation District (NSD) has successfully opened a FOG receiving station at its Soscol Water Recycling Facility. This allows local grease haulers to save time and money by dropping loads in Napa, rather than making the drive to the nearest receiving station in Oakland. The benefit to NSD is that methane gas created when the FOG is broken down in the treatment process can be collected and used to generate electricity.

Wastewater treatment is a very energy intensive process, with the District paying PG&E over $700,000 last year. Prior to opening the FOG receiving station, NSD was able to generate just under 30% of its energy needs for the treatment plant with the methane generated during wastewater treatment. Adding FOG to the treatment process bumps up methane production. “With the methane produced by one gallon of FOG, we can generate about $0.05 worth of electricity,” explains Jim Keller, NSD treatment plant manager. “It’s another case of “waste” becoming a resource.”

To insure a consistent and adequate flow of FOG, the District created tiered rates, so that the more FOG a hauler brings to NSD, the less the hauler pays per gallon. “If a hauler delivers over 50,000 gallons during the month, their deliveries are free,” points out Tim Healy, General Manager. “The most a hauler would pay is $0.10 per gallon, which is comparable to what other nearby receiving stations charge.” It appears that the new service and pricing strategies are popular; the amount of FOG received in April 2013 was almost double the amount received in March 2013, with May on track to be even higher. NSD expects to save over $100,000 this next year in electricity bills because of the FOG receiving station.


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